This invention relates to a pneumatic plant-blade-from-stem separator, usable preferably in the processing of tobacco for cigarette manufacture.
As is known by those skilled in the art, in manufacturing cigarettes, a tobacco leaf today must have its stems removed, that is, the stem (petiole) separated from the blade (lamina). Leaf material, in a mixed state, is fed to a separating machine, from which the blades emerge at one side and the stems at the other.
Previously used processes for performing the above operation were unsatisfactory and, to provide a more efficient method therefor, the applicant has developed a machine and process to separate fragments of plant-material leaf blades (laminae) comminuted from the stem (petioles), which was the object of IP 8403264, in which some improvements were later introduced, as described in patent application IP 8704253, contemplating more enhanced operation thereof.
The machine covered by the above-mentioned patents is essentially comprised by an upright box arrangement, provided with a lower lateral air inlet emerging under a transverse and perforated conveyor mat, which was replaced by a tilted and transverse plate, provided with numerous holes. According to IP 8704253, the perforated plate is disposed at an angle, with the highest end over the air inlet and the lowest end adjoining an outlet for rejected stems.
Notwithstanding the good performance of this machine, it was found that, prior to the improvement described in IP 8704253, the stems became stuck in the holes of the mat and were carried to the underside thereof. The stems remained at the underside obstructing air circulation and, consequently, reduced the pneumatic transportation of blades to be separated, giving rise to the need for frequent cleaning of the lower chamber of the separator, as well as of the chains of the mat, with the latter mechanism further being subject to wear and tear.
Accordingly, for the purpose of overcoming such inconveniences, the improvements described in IP 8704253 were incorporated in the machine, namely, inclusion of a perforated and tilted plate in lieu of the conveyor mat. Thus, wear due to nonexistence of moving parts was eliminated enabling the machine to operate with less installed power, since a motor was no longer required for the mat.
Nevertheless, it was also found that, due to the round shape of the holes, some of the stems became lodged in the holes, to a point where the bed became obstructed. Furthermore, as the air is recirculated in this equipment with dust and small particles PG,4 of blades being carried along, this material clung to the bottom of the perforated plate and was capable of totally or partially impeding pneumatic transportation of the blades being separated, which is a definite drawback from the standpoint of yields in the separating operation.
It should further be stressed that it would not be feasible to simply increase the diameter of the holes in the plate to prevent obstruction, since this would allow the stems to slip through, or these would clog the holes.